Electric switch



J. J. ZELLER ELECTRIC SWITCH Nov. 13, 1951 4 Sheets-Sheet 1 Filed June29, 1949 Nov. 13, 1951 J. J. ZELLER 2,574,770

ELECTRIC SWITCH Filed June 29, 1949 4 Sheets-Sheet 2 M mum l||||||||l|Illlllllllll 4015i: .5. I g w [27 NH C i & 1 JUEEIJZEZ/ M 3 1: 3

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,[JZQ/ZEF 4 Sheet'sSheet 3 I III Jage J. J. ZELLER ELECTRIC SWITCH Nov.13, 1951 Filed June 29, 1949 NOV. 13, 1951 J J ZELLER 2,574,770

ELECTRIC SWITCH Filed June 29, 1949 4 Sheets-Sheet 4 A HHHI FLO/7 TACTl/A TED I 7 Patented Nov. 13, 1951 ELECTRIC SWITCH Josef J. Zeller,Wauwatosa, Wis., assignor to Square D Company, Milwaukee, Wis., acorporation of Wisconsin Application June 29, 1949, Serial No. 101,985

This invention relates to electric switches and refers particularly topressure switches of the type used with air compressors and water pumps,but capable with slight modification of being float actuated to maintaina predetermined level of liquid in a tank.

One of the objects of this invention is to provide a switch .of thecharacter described which will function equally well when used either asa float switch or as a pressure switch despite the fact that in the onecase the actuating force is relatively slight while in the other it maybe very substantial.

In this connection it is more specifically an object of this inventionto provide'an electric switch which will snap open and shut with apositive action regardless of the service for which it is used.

A further object of this invention to provide an improved manner ofincorporating a pressure differential spring in a switch of this type,and whereby adjustment of the differential spring in nowise affects theoperation of the switch except to the extent that it either increases ordecreases the diiierential between the opening and closing pressures.

Another object of this invention is to provide an improved manner ofimparting opening and closing motion to the carrier of the movableswitch contacts from the slow movement of the actuating mechanism.

In this connection it is another object of this invention to provide aswitch of the character described in which the desired snap action isachieved through use of a bowed leaf spring reacting between two pivotedlevers one of which is pivotally connected to the actuating member sothat slow movement of the actuating member rocks the same to carry theend of the bowed spring attached thereto across dead center to therebysnap the contact carrier from one position to the other.

Another object of this invention is to provide a switch of the characterdescribed which when float actuated includes means to assure againstdiminishing or indecisive contact pressure as the float gradually risesand the switch tripping point is approached.

A still further object of this invention is to provide a switch of thecharacter described which has a far more lively action than switchesheretofore available for this service, and which by its design andconstruction is exceptionally flexible and may be readily applied todifferent types of service.

With the above and other objects in view, which will appear as thedescription proceeds, this inventidn resides in the novel construction,com- 7 Claims. (01. 200-83) 1 pressure source.

ment of the hereindisclosed invention may be made as come within thescope of the claims.

The accompanying drawings illustrate one complete example of thephysical embodiment of the invention constructed according to the bestmode so far devised for the practical application of the principlesthereof, and in which:

Figure 1 is a side view of a switch embodying this invention, said viewshowing the switch housing and diaphragm in section and illustrating theswitch in its normally closed condition;

Figure 2 is a view similar to Figure 1 but showing only the essentialparts of the switch mechanism, with the switch held open by pressure onthe underside of the diaphragm;

Figure 3 is a horizontal sectional view through Figure l on the plane ofline 3-3;

Figure 4 is a front view of the switch showing part'of the main springbroken away and illustrating particularly the manner in which thedifferential spring is incorporated in the assembly.

Figure 5 is a horizontal sectional view through Figure 4 on the plane ofthe line 5-5 Figure 6 is a view partially in side elevation andpartially in longitudinal section illustrating the switch adapted forfloat actuation; and

Figure 7 is a sectional view taken through Figure 6 on the plane of theline l'l.

Referring now particularly to the accompanying drawings in which likenumerals indicate like part throughout the several views, the numeral 5designates a generally U-shaped main frame for the switch mounted in ahousing 6.

If the switch is to be fluid pressure actuated as, for instance, in air.compressor or water pump service, a diaphragm l is secured acros a holein the bottom wall 8 of the housing by being clamped between the housingbottom wall and a diaphragm head 9. The interior of this head provides adiaphragm chamber connectable with the If the switch is to be floatactuated the diaphragm head is replaced by a pair of laterally spacedbrackets I 0 between which a lever H is pivoted as at !2, a shown inFigures 6 and 7.

In either case motion is adapted to be imparted to a main lever l3 toactuate the switch mechanism and to open and close the switch which isindicated generally by the numeral l4.

As is customary the switch M has pairs of cooperating stationary andmovable contacts l5 and 55 respectively, the former mounted upon aninsulated terminal block l1 and the latter upon an insulated carrier ISwith individual contact springs I3 for each pair thereof. The terminalblock is suitably secured to the main frame 5 by screws which passthrough a boss 2| on the underside of the terminal head and are threadedinto ears 22' extending in from the upperfront portion of the main frameside Walls 23. This manner of mounting the terminal head facilitates theadaptation of the switch to either normally open or normally closedservice.

The main frame 5 is a stamping and in addition to its side walls 23which have their front edge portions cut out as at 24, it includes abottom wall 25, the front and back portions of which are offsetdownwardly to provide feet upon which the switch mechanism rests. Theseflat supporting feet are seated upon the bottom wall of the housing 6above the front andfback marginal portions of the diaphragm 1 and aresecured in place by screws 25 which pass through the marginal edgeportion of the diaphragm head 9, the diaphragm and the bottom wall 8 ofthe housing to be threaded into the feet.

At its foremost portion the frame 5 has an inclined upwardly directedlip 21 to which a U shaped bracket 2B i secured. The sides of this Ll-shaped bracket have aligned notches 29 facing rearwardly. The forepartof theframe also has a lateral projection 31.! at one side thereof twhich an upright stem 3| is secured in parallel spaced relation to alonger upright stem 32 also anchored to the forenar't of the framemedially between the two arms of the ll-shaped bracket 2-8. The longerstem 32 has a main spring 33 mounted thereon while the shorter stemmounts a differential spring 34. This diiierential spring is normallyconfined between a shoulder .35 on the stem 3| and an adjusting nut 35threaded to the upper end of the stem.

The main spring 33 is confined between an adjusting nut :31 threaded onthe upper portion of the stem 32 and a shelf 38 resting upon the freeend of the main actuating lever 13 to thus at'all times ,yieldingly urgethe lever downwardly.

For float actuation neither of the springs just mentioned is required.Hence, these-elements are omitted when the switch is to .be floatactuated.

The main actuating lever -|3"is received-between the side walls 23 ofthe mainframe 5 and is pivotally connected thereto by a cross pin 39 ata point near the lower rear portion of the frame. The main actuatinglever I3 is a U-shaped stamping with its flanges 40 lying closelyadjacent to the inner surfaces of the frame side walls. Its web 4| hasV-shaped indentations 12 against which pointed fingers 43 extending upfrom a diaphragm plate 43 bear to lift the main lever against the oposition of the spring 33 in response to pressure in the diaphragmchamber, the fingers 43 passing through holes- .4 in the main frame.

Each side wall 23 of the main frame has a hardened plate 45 accuratelylocated thereon and riveted thereto. The front marginal edge .of eachplate Q5 has a V-shaped notch 46 therein in line with the cutout :24 ofthe side walls of the frame proper. These .notches 45 ;are transverselyaligned and receive knife edges 41 projecting rearw-ardly from thecontact carrier l-B.

For all intents and purposes, the plates '45 constitute part of the mainframe -5 and are separate pieces only to obviate the .need for hardeningthe entire frame to secure desired hardness for the :notches 4.5. Beingfiat pieces the lates 45 may be hardened without danger of deformation,as is also the case of the separate U-shaped clip 28.

The contact carrier I8 is preferably made up of two sheet metalstampings 48 and 59 riveted together as at 50. The stamping 48 isessentially a fiat lever and has the knife edges 4'! formed directlythereof while the stamping 49 is generally a 'U-shaped structure and hasan insulated contact carrying arm 5| secured thereto.

By virtue of the engagement of the knife edges .41 in the notches 46 thecontact carrier is rockably supported for movement between switch openand switch closed positions, these limits of motion being defined by thecollision of a laterallyprojeetin'g arm 52 on the lever 48 with eitherof two stop abutments 53 and 54 both of which are formed as part of theadjacent side wall of the main frame 5.

The arm 52 also provides means for opening a pressure relief valve 55(shown in light lines in Figure 4) as the switch is opened. Such reliefvalves are customarily employed where the switches are used for thecontrol of air compressors and have as their purpose to bleed pressurefrom the pressure chamber of the compressor as the compressor stops sothat subsequent starting of the compressor will be easier.

Up and down movement of the main actuating lever |3 is imparted to thecontact carrier H3 in a novel manner (now about to be described) whichassures a more lively switch action and generally improves the operationof the switch. It will be noted that the notches 46 and the notches 29are opposed to each other, that is, they face each other. The lever 48,which forms part of the contact carrier, is pivoted in the notches 4eand extends forwardly toward the other set of notches 29. Hence, itprojects toward an intermediate lever 55 which is embraced by the armsor flanges of the main actuating lever l3 and is pivotally connectedthereto as at 51, the pivot being a pin mounted in appropriate holes inthe side flanges or arms of the lever I3 and passing through slightlyelongated holes 58 in downstruck ears 59 on the intermediate lever 56,the major axis of the elongated holes 58 being parallel with the lever55.

The lever 56 has knife edges 60 received in the notches 29 and the rearend of the lever opposite its "knife edges has a spring seat 5| formedthereon. This spring seat is parallel to and spaced a short distancefrom a similar spring seat 63 on the lever 48. A bowed leaf spring 63has its ends hooked onto these spring seats 5| and 52 and yieldinglyurges the same apart. Hence, the bowed spring 63 holds the knife edges4! of the contact carrier in their notches l6 thereby retains thecontact carrier in position and also holds the knife edges 60 of theintermediate lever 56 in their notches '23. Also, depending upon whetheror not the pivot 51 is above or below the dead center plane joining thebottom of the notches 29 with the axis of the pivot 39, the bowed leafspring 63 holds the contact carrier in its switch open or switch closedposition respecti-vely.

Thus as shown in Figure l as long as the main lever 1| 3 is held down bythe spring .33 and the pivot axis 51 is below the defined dead centerplane'the spring seat 6| will be below the dead center plane joining thebottoms of the notches 29 and 46 and this disposition of the spring seat5:! so directs the thrust .of the bowed spring that the contact carrieris yieldingly urged thereby to its switch closed position shown inFigure 1.

As the pressure within the diaphragm chamber overbalances the force ofthe spring 33 and the actuating lever l3 moves upward the pivot 57crosses dead center and thereby swings the intermediate lever 56 on itsknife edges 60 to the position shown in Figure 2 at which the springseat 6| is above the dead center plane joining the bottoms of thegrooves 29 and 46. With such reversal of the position of the spring seatBl the thrust of the bowed spring 63 snaps the contact carrier to itsswitch open position shown in Figure 2. The described relative motionbetween the main lever l3 and the intermediate lever 56 is permitted bythe elongated shape of the openings 58.

The differential spring 34 by which the differential between thepressures at which the switch is opened and closed may be adjusted, isso incorporated in the mechanism as to assure against the possibility ofits presence and adjustment affecting the action of the switch inanywise. Hence, the shelf 38 upon which the main spring bears has an arm65 projecting from one end thereof and apertured to loosely receive thestem 3!. When the main lever I3 is in its lowest position in which it isnormally yieldingly held by the spring 33, the top of the arm 65, whichpreferably has two radial ridges 66 at diametrically opposite sides ofthe stem 3|, is spaced from the washer 61 interposed between the bottomof the differential spring 34 and the shoulder 35. Consequently, themain lever l3 may be lifted for a distance without opposition from thedifferential spring, and since the differential spring always bottoms onthe shoulder 35 before the main lever descends far enough to trip theswitch closed, closure of the switch takes place at a pressuredetermined solely by the setting of the main spring.

On the other hand, durin elevation of the main lever 13 to trip theswitch open, the diiferential Spring 34 is lifted off the shoulder 35and the load thereof added to that of the spring 33 before the lever l3has risen high enough to trip the switch. The differential spring thusacts only during opening of the switch and thereby determines thedifferential between the pressures at which the switch opens and closes;the greater the tension on the spring 34, the higher the pressure neededto open the switch. Therefore, by increasing the tension on the spring34, which is done by tightenin the adjusting nut 36, the

span or differential between the opening and closing pressures isincreased and vice versa.

Attention is directed to the manner in which the shelf 38 is constructedand mounted upon the free end of the lever 3. It is conveniently made asa channel shaped stamping having upwardly pressed knobs 68 positioned toproperly center the main spring and slots 69 in its. web to receiveupstanding tongues 70 on the flanges of the actuating lever. Forwardlyand rearwardly of the tongues the flanges of the actuating lever havebearin shoulders H upon which the shelf 38 rests.

The strength of the bowed spring 63 depends upon the service for whichthe switch is to be used. For air compressors where the opening of theswitch is accompanied by the actuation of a pressure relief valve thebowed spring must have maximum strength. ;For water systems where theopening of the switch does not entail concomitant actuation of apressure relief valve and between the levers.

where the pressures involved are generally less than that encountered inair compressor service, a medium strength spring is used. For floatactuation a still lighter spring is employed.

When the switch is adapted for float actuation the diaphragm chamber,the main sprin 33 and the pressure differential spring 34 are omitted.Consequently, the only force holding the pivoted main actuating lever 13down is that derived from the relatively light bowed spring 53. Thespring 63' thus, of course, also provides the contact pressure to holdthe contact carrier IS in its switch closing position.

As noted hereinbefore, in this embodiment of the invention a float leverH is pivotally mounted on the underside of the switch and this lever,which may be considered the actuator proper, has a motion transmittingconnection with the pivoted lever 13 so that as the lever H moves up anddown with the float it will impart similar movements to the lever 63.The pivot l2 for the lever ll may be either rearwardly or forwardly ofits connection with the lever i 3, the former condition beingillustrated in Figure 6. In this case ascent of the float lifts thelever l3 to effect opening of the switch and descent of the float lowersthe lever 13 to effect closure of the switch.

If the pivot pin I2 is moved from its position shown in Figure 6 andinstead passed through a second set of holes and 75 respectively in thebrackets Hi and the head of the lever II, the reverse condition obtains,i. e., ascent of the float closes the switch and vice versa.

The motion transmitting connection between the levers II and i3comprises two parallel transversely spaced links ll pivoted as at 18 tothe lever l3 and to the lever II by means of a cross pin 19. The crosspin 19 passes through holes in the lower ends of the links T! and theflanges ll of the U-shaped head of the float lever l I.

The clearance between the pin 19 and the holes in which it seats ispurposely large to provide a degree of lost motion in the connection Aslong as the lever II is in its lowermost position this lost motion istaken up by the weight of the lever. As the float lever ll rises thelost motion or play, of course, must be taken up in the other directionbefore motion is transmitted to the lever I3.

The limited freedom for independent motion between the levers I! and [3resulting from this play in the connection therebetween enables a coilspring confined between the bottom of the lever 13 and the pin 19 toassure the desired decisiveness in switch action despite the relativeweakness of the spring 63. A bridging piece 8| resting upon the flangesI I of the float lever and provided with a hole 82 holds the lower endof the coil spring in position bearing upon the cross pin 79, while theupper end of the spring is received in the depressed pocket in thebottom of the lever I 3.

The manner in which the spring 80 precludes indecisive contact pressureis as follows: Without the spring 80 and the play or lost motion whichit can take up, as the lever I3 rises a point is reached where thecontact pressure provided by the light leaf spring 63 balances thecontact springs l9 and the contacts begin to ease off. However, with thecoil spring 30 before this point of balance is reached the force storedin the spring 80 overcomes the spring 63' and by 75 virtue of the playor lost motion in the connecagar 7220 7 .tion :between the levers II:and 13 snaps "the switch open.

From the foregoing. description taken in connection withthezaccompanying drawings it will be readily apparent to those skilledin the art that this invention :provides "a switch which is .verywelladapted for either pressure .or float actuation and that it possessesmany advantages over switches heretofore available for this purpose.

What I -claim as .my .invention is:

l. lInian electric snap switch adapted for pressure and. floatactuation: a 'frarne providing opposed knife edge seats; a contactcarrier having knife :iedges engaging one of said seats, .said:contact-carrier:carryingithe movable contacts of the switch :formovement to and from switch closing position by rocking motion aboutitsknife edges; an intermediate, lever havingknife edges engaging'theother of said knife edge seats, said con- :tact barrier and intermediatelever extending from :their respective knife edges towards each otherand having adjacent but spaced .apart spring seats; a spring tensionedbetween said spring seats and ,-yieldingly urging said. spring seatsapart and to opposite sides of a dead center plane connecting theopposed knife edge seats; and an actuating lever pivotally mounted uponthe :frame and having pivotal connection withthe intermediate lever sothat-rocking of the actuatinglever-about its pivotal connection with theframe-swings *the intermediate lever about its knife edges to open andclose the switch.

2. In an electric switch of the character described: a frameincludingspaced side walls provided with notches inthe front edges thereof; acarrier for the movable contacts of the switch having knifevedgesreceived insaid notches; an actuating lever flietween the side walls ofthe frame and pivoted thereto, the free'end of the actuating leverextending beyond the notched front edges of the side walls and beyondthe contactor carrier pivoted therein; an intermediate lever :mediallypivotally connected to the free end portion of the actuating lever;knife edges-on the end of the intermediate lever nearest :the free endof the actuating lever; means on the adjacentportion of the frameproviding notches in which said last named knife edges are received; aspring seat on the inner end of the intermediate lever; a spring'seat onthe contactor carrier facing the spring seat on the intermediate lever;and a spring tensioned between said seats and urging them apart to thussnap the contactor carrier from one position to the other as theactuating lever swings on its pivot to carry its connection with theintermediate lever across dead center, the pivotal connection betweenthe intermediate lever and the actuating lever having sufficient 110stmotion to enable said connection to swing across dead center as theactuating lever swings on its pivot.

3. In a snap switch of the character-described: a frame having twopairsof knife edge receiving notches. spaced apartand facing each other;a carrier for the movable contacts of the switch having knife edgespivotally received in one of said pairs of notches and adapted to carrythe movable contacts of the switch from one position to the other assaid carrier rocks upon its knife edges; means for defining the limitsof said rock- ;movement; a main lever pivotally connected to the frameadjacent-to said pair of notches in which "the knife edges of thecontact carrier are pivoted, the free end of said lever being adjacentto the "other pair .;of notches; an intermediate lever having knifeedges pivotally engaged in said-other pair of notches andextendingztherefrom toward the first pairof notches; :meansv pivotallyconnecting said'intermediate lever medially ofits ends'tothefree endportion .ofthelmain lever; spring seats 'on the intermediate lever andthe contact carrier spaced apart but facing each other; and a bowedspring confined between said spring seats to yieldin'gly'urge the sameapart and thus hold thecontactparrier at one or the'other of its limitsof movement dependinguponthe position of the mainand-intermediaterlevers.

4. The switch of claim Bfurther characterized by the provision-of acompression spring acting upon the main lever-andproviding a forcetending to rock the lever about its pivotalconnection with the-frame inone direction; and fluidpres- .sureiresponsive means acting upon themainlever and providing a force tending to rock the lever in theopposite "direction.

5. In a switch of the character described: *a frame having spacedsidewalls, saidside walls having-knife-edge receiving notches opening :tothe front of the frame; means on the forepart of the frame providinganother set of knife edge receiving notches facing rearwardly toward thefirst designated set of notches; a carrier forthe movable contacts ofthe switch having'knife edges received in the first designated notchesto mount the contactcarrier forrocking motion; means defining the limitsof said rocking motion; a main lever betweenthe side walls of theframe'and-piv oted thereto on-an axis spaced rearwardly and downwardlyfrom the first designated knife edge receiving notches with the free endof the lever adjacent to said other setof notches at the forepart of theframe, said lever having transversely spaced arms; an intermediate leverembraced by the arms of "the main lever and medially pivotally connectedthereto near the free -endof the main lever; knife edges on theintermediate lever engagingin the set of notches at the forepart of theframe; a spring seat on the intermediate lever rearwardly of its pivotalconnection with the main lever; a spring seat on the contact carrierfacing the spring seat on'the intermediate lever; and a bowed'leafspring having its free ends bearing against the spring seats toyieldingly urge the same apart and thereby :hold the knife edges of thecontact-carrier in their respeotive notches and yieldingly hold thecontact carrier in one or the other of its llil'llts'df rocking motiondepending upon the position of the main and intermediate levers.

6. In a-switch of the character described: a movable contact having acontact spring which is tensioned as the switch is closed; a pivotedactuating lever; mechanism connected between the movable contact and theactuating lever for snapping the movable contact from one position tothe other as the actuating lever rocks on its pivot, said mechanismincluding a 'bowed spring which holds the movable contact in its closedposition and thereby tensions the contact spring; an actuator; a motiontransmitting connection between the actuator and said pivoted actuatinglever, said motion transmitting connection having a degree of lostmotion; and a spring reacting between the actuator and the pivotedactuating lever and yieldingly urging said members apart so that duringmovement of the actuator toward the pivoted'actuatmg'lever the lostmotion in the connection is taken up before movement is imparted to-thepivoted actuating lever, -and'fcrc'e is stored in said spring to snapthe switch open before the instant is reached at which the forces of thecontact spring and the bowed spring would balance.

7. In a switch of the character described: a frame; a main lever pivotedat one end portion to the frame, said main lever having spaced apartopposing flanges thereon extending to its other end portion and disposedto swing edgewise with the main lever; an intermediate lever receivedbetween the flanges on said other end portion of the main lever; apivotal connection between one end of said intermediate lever and theframe adjacent to said other end portion of the main lever; a motiontransmitting connection between the main and intermediate levers wherebypivotal motion of the main lever is translated into rocking motion ofthe intermediate lever about its pivotal connection with the frame;switch means connected with the opposite end of said intermediate leverto be actuated thereby between switch-open and switch-closed positions;a bridge-like saddle overlying the intermediate lever and said other endportion of the main lever, said saddle seating upon edge portions of themain lever flanges; an interlocking connection between each of saidflanges and the saddle hold- 10 ing the latter against movement relativeto the main lever except in a direction to lift the saddle ofi of saidedges of the main lever flanges; and a spring acting upon said saddle tohold the same against movement relative to the main lever in saiddirection to thus maintain the saddle operatively connected with themain lever, said spring acting through the saddle to apply a force onthe main lever yieldingly urging the same and the intermediate leverconnected therewith toward a position at which said switch meansactuated by the intermediate lever is at one of said switch positions.

J OSEF J. ZELLER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,610,213 De Ville Dec. 7, 19262,083,343 Naul June 8, 1937 2,157,156 Abendroth May 9, 1939 2,255,115Helle Sept. 9, 1941 2,453,861 Rothwell Nov. 16, 1948

